docs: def add_port_to_free_pool(self, port):
          """Add a new port to the free pool for allocation."""
          if port < 1 or port > 65535:
              raise ValueError(
                  'Port must be in the [1, 65535] range, not %d.' % port)
          port_info = _PortInfo(port=port)
          self._port_queue.append(port_info)